1. Field of the Invention
The present invention relates to a paper machine, and, more particularly, to a former for manufacturing premium tissue and toweling, and also relates to a former which utilizes a belt press in a paper machine. The present invention relates to a twin wire former for manufacturing premium issue and toweling which utilizes a belt press in a paper machine. The system of the invention is capable of producing premium tissue or toweling with a quality similar to a through-air drying (TAD) but with up to a 40% cost savings.
The present invention also relates to a twin wire former ATMOS system which utilizes a structured fabric which has good resistance to pressure and excessive tensile strain forces, and which can withstand wear/hydrolysis effects that are experienced in an ATMOS system. The system also includes a permeable belt for use in a high tension extended nip around a rotating roll or a stationary shoe and/or which is used in a papermaking device/process, and a dewatering fabric for the manufacture of premium tissue or towel grades without utilizing a through-air drying (TAD) system. The fabric has key parameters which include permeability, weight, caliper, and certain compressibility.
2. Description of the Related Art
In an ATMOS system, a sheet is formed on a structured or molding fabric and the sheet is further sandwiched between the structured or molding fabric and a dewatering fabric. The sheet is dewatered through the dewatering fabric and opposite the molding fabric. The dewatering takes place with air flow and mechanical pressure. The mechanical pressure is created by a permeable belt and the direction of air flow is from the permeable belt to the dewatering fabric. This can occur when the sandwich passes through an extended pressure nip formed by a vacuum roll and the permeable belt. The sheet is then transferred to a Yankee by a press nip. Only about 25% of the sheet is slightly pressed by the Yankee while approximately 75% of the sheet remains unpressed for quality. The sheet dried by a Yankee/Hood dryer arrangement and then dry creped. In the ATMOS system, one and the same structured fabric is used to carry the sheet from the headbox to the Yankee dryer.
International Publication No. WO2005/075736, the disclosure of which is hereby expressly incorporated by reference in its entirety, discloses an ATMOS system which uses a belt press and which can utilize a twin wire configuration. However, this document does not address the advantages of utilizing differential speeds between a forming belt and a structured fabric according to the invention.
U.S. Pat. No. 4,440,597 to WELLS et al., the disclosure of which is hereby expressly incorporated by reference in its entirety, and, in particular, the Abstract of this document, discloses a process that utilizes a differential velocity transfer of a wet-laid embryonic web having relatively low fiber consistency from a carrier to a substantially slower moving, open-mesh transfer fabric having a substantial void volume. The web is then dried while precluding substantial macroscopic rearrangement of the fibers in the plane of the web. The differential velocity transfer is effected without substantial compaction of the web by avoiding substantial mechanical pressing, centrifugal slinging, air blasting, and the like.
International Publication No. WO 2005/075732, the disclosure of which is hereby expressly incorporated by reference in its entirety, discloses a belt press utilizing a permeable belt in a paper machine which manufactures tissue or toweling. According to this document, the web is dried in a more efficient manner than has been the case in prior art machines such as TAD machines. The formed web is passed through similarly open fabrics and hot air is blown from one side of the sheet through the web to the other side of the sheet. A dewatering fabric is also utilized. Such an arrangement places great demands on the forming fabric because the pressure applied belt press and hot air is blown through the web in the belt press. However, this document does not address the advantages of utilizing differential speeds between a forming belt and a structured fabric according to the invention.
International Publication No. WO2005/075737, the disclosure of which is hereby expressly incorporated by reference in its entirety, discloses a structured molding fabric which can create a more three-dimensionally oriented sheet.
The disadvantages of systems of the type disclosed in International Publication No. WO2005/075736 which use a twin wire former is that the sheet is not formed on a structured fabric. Instead, the sheet is formed between inner and outer forming fabrics and then transferred via the inner forming fabric to a structured fabric without utilizing differential speeds. As a result, the voids of the structured fabric are not filled up with fibers as when the web is formed over a structured fabric. The more the voids are filled with fibers, the greater is the mass of un-pressed fibers at the Yankee and the higher the quality of the sheet.